The present invention relates to a portable-type position determining system and a receiving system, and more particularly to a position determining system and a receiving system capable of receiving GPS electric waves which are sent from GPS (Global Positioning System) satellites.
Conventionally, a position determining system which uses information sent from GPS satellites and which is held by a movable object, such as a user, etc. determines the position of the movable object, by receiving information regarding the determined positions. The information regarding the determined positions are navigation signals, such as ephemeris data, almanac data, etc. The ephemeris data are orbital information representing orbit into which a satellite is put or correction information used for time correction. The almanac data are schematic orbit information representing the entire satellites. To receive data from the respective GPS satellites, it is necessary that a timing of sending data from the respective satellites coincides with a timing of receiving such data. The timing of sending data at all times varies, since the GPS satellites or the position determining systems at all times shift from place to place. Therefore, in car navigation systems using the GPS, the timing of sending data from the satellites at all times coincides with the timing of receiving such data, thereby a position determination process can continuously be performed.
However, if the same position determination process as that performed in car navigation systems is performed in a position determining system which is of a battery-powered wristwatch type and of a portable type, a drawback arises in that the battery life of such a small-size position determining system is expected short. For the purpose overcoming the above drawback, the large volume of battery may be employed, resulting in another problem that the small-size position determining system is manufactured large in size.
Accordingly, the present invention has been made in consideration of the above, and an object thereof is to provide a position determining system, a receiving system, a method of determining the position of a movable object and a method of receiving data regarding the position, wherein unnecessary position determination processes are eliminated.
Another object of the present invention is to provide a position determining system, a receiving system, a method of determining the position of a movable object and a method of receiving data regarding the position, which appropriately achieve a reduction in power consumption.
According to one aspect of this invention, there is provided a position determining system comprising:
a receiver which receives position information sent from GPS satellites;
a position determining unit which determines a position of the receiver based on the position information received by the receiver;
a display unit which displays the position of the receiver which is determined by the position determining unit; and
a controller which controls a time interval at which the position of the receiver is determined by the position determining unit, in accordance with a resolution of an area between predetermined positions displayed on the display unit.
In this structure, in a state where the determined position is not displayed on the display unit, the position determining unit is not required to perform unnecessary position determination processes.
According to another aspect of this invention, there is provided a position determining system comprising:
a receiver which receives position information sent from GPS satellites;
a position determining unit which determines a position of the receiver based on the position information received by said receiver;
a display unit which displays the position of the receiver which is determined by said position determining unit; and
a controller which controls a time interval at which the position of the receiver is determined by said position determining unit, based on a reduced scale of a display screen on which the position of the receiver is displayed.
According to another aspect of this invention, there is provided a position determining system comprising:
a receiver which receives plural pieces of position information which are sent from a plurality of GPS satellites;
a position determining unit which determines a position of a movable object based on the plural pieces of position information which are received by the receiver; and
a controller which determines an appropriate number of GPS satellites from the plurality of GPS satellites which send the plural pieces of position information to be received by the receiver. In the structure, a desired number of GSP satellites are set when the position determining unit determines the position of the movable object. Thereby, the electric power to be consumed by the receiver when determining its own position can be eliminated.
According to still another aspect of this invention, there is provided a receiving system comprising:
a receiver which receives position information sent from GPS satellites;
a position determining unit which determines a position of the receiver based on the position information received by the receiver; and
a controller which controls an interval at which the position determining unit determines the position of the receiver, in accordance with an output of a power source which supplies electrical power to the receiver and the position determining unit. In such a structure, the load onto the receiver may become light in accordance with the remaining battery.
According to yet still another aspect of this invention, there is provided a receiving system comprising:
a receiver which receives position information sent from GPS satellites;
a position determining unit which determines a position of the receiver based on the position information received by the receiver; and
a controller which turns off a power supply to the receiver and the position determining unit when a predetermined time period lapses after the position determining unit determines the position of the receiver. In this structure, immediately after the receiver receives the position information, the electric power to the receiver is broken, thereby saving the consumption power.
According to a further aspect of this invention, there is provided a receiving system comprising:
a receiver which receives plural pieces of position information which are sent from a plurality of GPS satellites;
a position determining unit which determines a position of a movable object based on the plural pieces of position information received by the receiver;
a storage unit which stores calculation data regarding leap seconds which are necessary for correcting a satellite time sent from the plurality of GPS satellites. In such a structure, the receiver may not receive the calculation data regarding the leap seconds, thereby saving the consumption power.
According to a still further aspect of this invention, there is provided a method comprising:
receiving position information sent from a plurality of GPS satellites;
determining a position based the received position information; and
controlling a time interval, at which the position is determined, in accordance with the determined position. With this method, in a state where the determined position is not displayed by the displaying step, unnecessary position determination processes are not performed by the position determining step.
According to a yet still further aspect of this invention, there is provided a method comprising:
receiving position information sent from a plurality of GPS satellites;
determining a position based on the received position information; and
determining an appropriate number of GPS satellites from the plurality of GPS satellites which send the position information to be received. With this method, the predetermined number of GPS satellites are set. Therefore, the receiving step may not perform unnecessary position determination processes during the time the position of the movable object is determined.
Broadly defined, the present invention provides a position determining system comprising:
a receiver which receives position information sent from GPS satellites;
a position determining unit which determines a position of the receiver based on the position information received by said receiver; and
a controller which controls a time interval at which the position of the receiver is determined by said position determining unit, in accordance with the detected position.